The present invention relates to the art of earth boring and, more particularly, to a rotary rock bit with improved means for retaining the cutter on the bearing pin. The present invention is especially adapted for use in that type of rotary rock bit popularly known as a rotary cone bit; however, its use is not restricted thereto, and the present invention can be used in other types of rolling cutter rock bits.
A rotary cone rock bit is adapted to be connected as the lowest member of a rotary drill string. As the drill string is rotated, the bit disintegrates the earth formations to form an earth borehole. The bit includes individual arms that extend angularly downward from the main body of the bit. The lower end of each arm is shaped to form a spindle or bearing pin. A cone cutter is mounted upon each bearing pin and adapted to rotate thereon. Individual bearing systems promote rotation of the cone cutters. The bearing systems have traditionally been roller bearings, ball bearings, friction bearings, or a combination of the aforementioned bearings. The cone cutters include cutting structure on their outer surfaces that serve to disintegrate the formations as the bit is rotated.
The rotary rock bit must operate under very severe conditions, and the size and geometry of the bit is restricted by the operating characteristics. Some means for locking the cone cutter on the bearing pin must be provided. Traditionally, the locking function has been performed by a ball bearing system. Other systems are known, for example, a roller bearing locking system. Such systems have not been entirely satisfactory.